The present invention relates to compositions and methods for minimizing adverse drug experiences associated with oxybutynin therapy. Accordingly, this invention covers the fields of pharmaceutical sciences, medicine and other health sciences.
Oral oxybutynin is currently used for treating various forms of overactive bladder and urinary incontinence. Particularly, oxybutynin effectively treats neurogenically caused bladder disorders. Relief from such disorders is attributed to the anticholinergic and antispasmodic action which oxybutynin imparts to the parasympathetic nervous system and the urinary bladder detrusor muscle.
It is generally believed that, while this anticholinergic activity contributes to oxybutynin""s clinical usefulness, it also contributes to certain uncomfortable adverse drug experiences such as dry mouth, dizziness, blurred vision, and constipation. More specifically, these experiences have been generally attributed to the presence and amount of active metabolites of oxybutynin, for example, N-desethyloxybutynin.
The above-referenced adverse drug experiences are observed in a majority of patients using current oxybutynin formulations. In some cases, these adverse experiences are severe enough to persuade the patient to discontinue treatment.
In view of the foregoing, compositions and methods for administering oxybutynin to help minimize the incidence and/or severity of the above-described adverse drug experiences are extremely desirable.
Accordingly, the present invention provides a method of minimizing an adverse drug experience associated with oxybutynin therapy which comprises the step of administering a pharmaceutical composition comprising oxybutynin to a subject such that the ratio of area under the plasma concentration-time curve (AUC) of oxybutynin to an oxybutynin metabolite is about 0.5:1 to about 5:1. The adverse drug experience may be any adverse experience resulting from administration of oxybutynin, for example, anticholinergic, and/or antimuscarinic in nature.
Specific examples of known oxybutynin adverse experiences include but are not limited to: gastrointestinal/genitourinary experiences, nervous system experiences, cardiovascular experiences, dermatological experiences, and opthalmic experiences, among others.
Delivery formulations useful in conjunction with the method of the present invention include but are not limited to: oral, parenteral, transdermal, inhalant, or implantable formulations. In one aspect of the invention, the delivery formulation is a transdermal delivery formulation.
Oxybutynin has a chiral molecular center, leading to the presence of (R)- and (S)-isomers. When metabolized, oxybutynin gives rise to metabolites such as N-desethyloxybutynin, which may also be present as (R)- and (S)-isomers or a combination thereof. The method of the present invention specifically encompasses each isomer for both oxybutynin and its any corresponding metabolites. For example, in one aspect, the mean plasma AUC ratio of (R)-oxybutynin to (S)-oxybutynin is about 0.7:1. In another aspect, the mean AUC ratio of (R)-N-desethyloxybutynin to (R)-oxybutynin is from about 0.4:1 to about 1.6:1. In one aspect, this mean AUC ratio may be about 1:1. In another aspect, the mean AUC ratio of (R)-N-desethyloxybutynin to (S)-N-desethyloxybutynin is from about 0.5:1 to about 1.3:1. For example, this mean AUC ratio may be about 0.9:1. In another aspect, the metabolite may have a mean peak plasma concentration of less than about 8 ng/ml.
A pharmaceutical composition for administering oxybutynin to a subject is also provided, comprising oxybutynin that provides an AUC ratio of oxybutynin to an oxybutynin metabolite of from about 0.5:1 to about 5:1.
Examples of suitable dosage formulations for the composition include: oral, parenteral, transdermal, inhalant, or implantable type compositions. In one aspect, the composition is a transdermal composition.
The compositions may contain oxybutynin in its various (R)- and (S)-isomeric forms, or mixtures thereof. Further, the compositions may include as well as (R) and (S)-isomeric forms oxybutynin metabolites. In one aspect of the present invention, the composition results in an (R)-oxybutynin to (S)-oxybutynin mean AUC ratio of about 0.7:1. In another aspect, the composition of the present invention results in an (R)-N-desethyloxybutynin to (R)-oxybutynin mean AUC ratio of from about 0.4:1 to about 1.6:1. In an additional aspect, this ratio is about 1:1. In another aspect, the (R)-N-desethyloxybutynin to (S)-N-desethyloxybutynin mean AUC ratio may be from about 0.5:1 to about 1.3:1. In one aspect, the ratio is about 0.9:1. In yet another aspect, the mean peak metabolite plasma concentration may be less than about 8 ng/ml.
The composition of the present invention may include a pharmaceutically acceptable carrier, and other ingredients as dictated by the particular needs of the specific dosage formulation. Such ingredients are well known to those skilled in the art. See for example, Gennaro, A. Remington: The Science and Practice of Pharmacy 19th ed. (1995), which is incorporated by reference in its entirety. For example, a transdermal formulation include, but not limited to, permeation enhancers, anti-irritants, adhesion adjusters, and combinations thereof.
There has thus been outlined, rather broadly, the more important features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. Other features of the present invention will become clearer from the following detailed description of the invention, taken with the accompanying drawings and claims, or may be learned by the practice of the invention.